1. Field of the Invention
The present invention relates to the molecular oxygen oxidation of a cycloalkane such as cyclohexane to produce a product mixture comprised of cycloalkylhydroperoxide wherein during the oxidation a vapor stream is removed from the oxidation zone, condensed and returned to the oxidation zone, the improvement being separation of cycloalkane oxidation products such as the hydroperoxide, cycloalkanol and cycloalkanone from the said stream before the stream is returned to the oxidation zone.
2. Description of the Prior Art
The oxidation of cyclohexane to form products including cyclohexylhydroperoxide (CHHP) is a known reaction.
U.S Pat. No. 3,927,115 shows the oxidation of cyclohexane with molecular oxygen to form CHHP, cyclohexane and cyclohexanone, the improvement being carrying out the oxidation in the presence of an alkane having a tertiary carbon, eg. isobutane.
U.S. Pat. Nos. 3,949,003 and 3,987,115 show the oxidation of cyclohexane in the presence of a tertiary alcohol and a tertiary hydroperoxide to produce CHHP, cyclohexanol and cyclohexanone.
U.S Pat. No. 3,949,004 shows oxidation of cyclohexane in the presence of a stabilizing agent such as water or tertiary butyl alcohol to produce CHHP, cyclohexanol and cyclohexanone.
U.S. Pat. No. 4,080,387 relates to oxidation of cyclohexane to a product mixture comprised of CHHP, cyclohexanol and cyclohexanone and to the concentration of CHHP by distillation procedures.
U.S. Pat. No. 2,675,407 describes the oxidation of a cycloalkane dissolved in tertiary butyl alcohol.
U.S. Pat. No. 2,851,496 describes the oxidation of cyclohexane including reacting the product mixture in the presence of a peroxide decomposition catalyst to reduce the CHHP content.
U.S. Pat. No. 3,365,490 relates to the production of adipic acid by oxidizing cyclohexane, separating the reaction mixture with recycle of unreacted cyclohexane and subsequent nitric acid oxidation of the cyclohexanol and cyclohexanone to form adipic acid.
U.S. Pat. No. 3,365,490 relates to the oxidation of cycloalkanes to hydroperoxides and includes a basic treatment of recycle cycloalkane.
U.S. Pat. No. 3,694,511 describes the hydrogenation of cycloalkane by peroxides under conditions effective to preserve catalyst life and activity.
U.S Pat. No. 3,719,706 separates by-products form cyclohexyl hydroperoxide by water washing.
U.S. Pat. No. 3,923,895 treats the hydroperoxide containing solution in cycloalkane by heating in the presence of a chromium catalyst in order to obtain cyclohexanone and cyclohexanol.
U.S. Pat. No. 3,927,108 is also concerned with the hydrogenation of cyclohexylhydroperoxide in the presence of a particular catalyst.
U.S. Pat. No. 3,957,876 describes preparation of CHHP by oxidation of cyclohexane containing a cobalt catalyst in a specially zoned oxidation reactor.
U.S. Pat. No. 4,326,084 shows oxidation of cyclohexane to produce a mixture containing CHHP and decomposing this latter material with a particular, designated catalyst.
U.S. Pat. No. 4,341,907 describes oxidation of cyclohexane in the presence of a particular heavy metal compound catalyst.
U.S. Pat. No. 4,465,861 describes decomposition of a reaction mixture containing a CHHP using a specified catalyst combination.
U.S. Pat. No. 4,482,746 likewise shows decomposition of CHHP using a special catalyst combination of components.
U.S. Pat. No. 4,499,305 similarly describes decomposition of CHHP using a special catalyst.
U.S. Pat. No. 4,503,257 decomposes CHHP by using a catalyst consisting of a certain metal on a solid support.
U.S. Pat. No. 4,720,592 describes extracting a cyclohexane oxidation mixture with water followed by hydrogenation to convert the CHHP.
U.S. Pat. No. 3,917,708 describes the oxidation of cyclohexane using a heavy metal salt catalyst.
U.S. Pat. No. 4,163,027 describes a process for working up cyclohexane oxidation mixture by treatment with alkaline metal compound containing solutions.
U.S. Pat. No. 4,543,427 shows decomposition of CHHP with a supported cobalt catalyst.
U.S. Pat. No. 4,704,476 describes working up a cyclohexane oxidation mixture with aqueous alkali solution.
U.S. Pat. No. 4,814,511 shows working up cyclohexane oxidation mixtures by reaction with cyclo-olefins in the presence of certain, designated catalysts with ultimate hydrogenation of the resulting oxide to the cycloalkanol.
CHHP has been suggested as a reactant for the catalytic epoxidation of olefinically unsaturated compounds such as propylene to form the corresponding oxirane compound. See for example, U.S. Pat. Nos. 3,983,143 and 3,870,729 as well as European Patent 0 129 814.
Generally, a mixture of oxygen and inert gas is employed as the oxidant feed to the oxidation. Air is especially preferred. Vapors are removed from the oxidation reaction zone in order to prevent inerts build-up and/or to remove the oxidation heat of reaction by vaporization of components of the liquid oxidation reaction mixture. In prior practices, the removed vapor is cooled by indirect heat exchange or by direct contact with cool liquid feed to the oxidation zone to condense the readily condensible components including cycloalkane, cycloalkylhydroperoxide, cycloalkanol and cycloalkanone, which are recycled to the oxidation reaction zone. See, for example, U.S. Pat. No. 3,109,864.
However, it has now been found that recycle of the oxidation products, removed as vapor, to the oxidation reaction zone after condensation results in a substantial decrease in oxidation reaction selectivity, especially to the cycloalkylhydroperoxide product.